Mononuclear cells modulate the activity of pancreatic stellate cells which in turn promote fibrosis and inflammation in chronic pancreatitis

Background

Interactions between mononuclear cells and activated pancreatic myofibroblasts (pancreatic stellate cells; PSC) may contribute to inflammation and fibrosis in chronic pancreatitis (CP).

Methods

Markers of fibrosis and inflammation were concomitantly analysed by immunohistochemistry in chronic pancreatitis tissues. In vitro, PSC were stimulated with TNFalpha and LPS. Primary human blood mononuclear cells (PBMC) and PSC were cocultured, followed by analysis of cytokines and extracellular matrix (ECM) proteins. PBMC were derived from healthy donors and CP and septic shock patients.

Results

In areas of mononuclear cell infiltration in chronic pancreatitis tissues, there was decreased immunoreactivity for collagen1 and fibronectin, in contrast to areas with sparse mononuclear cells, although PSC were detectable in both areas. LPS and TNFalpha induced collagen1 and fibronectin levels as well as the matrix degradation enzyme MMP-1. Coculture experiments with PSC and PBMC revealed increased fibronectin secretion induced by PBMC. In addition, donor and CP PBMC significantly induced an increase in IL-6, MCP-1 and TGFbeta levels under coculture conditions. Determination of the source of cytokines and ECM proteins by mRNA expression analysis confirmed PSC as major contributors of ECM production. The increase in cytokine expression was PBMC- and also PSC-derived.

Conclusion

Mononuclear cells modulate the activity of pancreatic stellate cells, which may in turn promote fibrosis and inflammation.

Periostin creates a tumor-supportive microenvironment in the pancreas by sustaining fibrogenic stellate cell activity

BACKGROUND & AIMS

Pancreatic cancer creates desmoplasia by stimulating stellate cells (PSCs), thereby influencing tumor aggressiveness. The aim of this study was to analyze the impact of the PSC-specific matrix protein periostin on tumor responses to radiochemotherapy.

METHODS

PSCs and cancer cells in primary and metastatic lesions of patients treated with or without neoadjuvant radiochemotherapy were evaluated by immunohistochemistry. Periostin messenger-RNA levels determined by quantitative reverse-transcription polymerase chain reaction were correlated to patient survival. Interactions between PSCs and cancer cells and the effects of periostin in modulating cellular responses under conditions of hypoxia, starvation, and radiochemotherapy were assessed by immunoblotting and by growth, clonogenicity, and invasion assays.

RESULTS

Periostin messenger-RNA levels were elevated 42-fold in cancer, and patients with increased expression had a tendency toward shorter survival (19 vs 12 months; P = .14). Stromal cells were the only source of periostin in the pancreas and in metastatic sites. Cancer cell supernatants stimulated periostin secretion from PSCs. Recombinant periostin increased alpha-smooth muscle actin, periostin, collagen-1, fibronectin, and transforming growth factor-beta1 expression while decreasing PSC invasiveness. These effects were reversed by silencing periostin expression and secretion by small interfering RNA transfection. In cancer cells, periostin stimulated growth and conferred resistance to starvation and hypoxia. In addition, the periostin downstream target collagen-1 significantly increased chemoresistance.

CONCLUSIONS

Once stimulated by cancer cells, PSCs remain active via an autocrine periostin loop even under radiotherapy and produce excessive extracellular matrix proteins, creating a tumor-supportive microenvironment. Increased periostin expression may therefore reflect a more aggressive tumor phenotype.